As a production method of peptide besides a solid phase method and a liquid phase method, a production method using a protecting group (hereinafter to be also referred to as an anchor group) permitting a reaction in a homogeneous liquid phase, and, after changing the solvent composition after the reaction, performing isolation and purification merely by filtration and washing (hereinafter to be also referred to as an anchor method) has recently been proposed. The anchor method is a production method of peptide, wherein, in peptide synthesis and the like, a particular compound that shows reversible changes between a dissolved state and an undissolved (precipitated) state according to the changes of the solvent composition is used as a compound (anchor) that forms an anchor group for protecting the C-terminal and/or a side chain functional group of amino acid or peptide. Here, the anchor group means a protecting group that binds to a reactive substrate to make the substrate soluble in nonpolar solvents and capable of reaction in a liquid phase, and that precipitates on addition of a polar solvent to enable solid-liquid separation, thus showing both reactivity and convenience of working up. The anchor means a compound for forming an anchor group.
For example, patent document 1 and non-patent document 1 each disclose a method of using 3,4,5-tri(n-octadecyloxy)benzyl alcohol as a protective reagent for carboxy group and the like. In addition, patent documents 2-4 each disclose anchors such as 3,5-di(docosyloxy)benzyl alcohol, 2,4-di(docosyloxy)benzyl alcohol, trityl type compound and the like.
The present inventors have also developed a particular diphenylmethane compound (patent document 5) and a fluorene compound (patent document 6) as an anchor usable for the anchor method.